Prostheses for intramedullary implantation in the bones of the metacarpophalangeal and proximal interphalangeal joints have taken a variety of forms, among these being onepiece elastic devices, such as those disclosed in the U.S. Pat. Nos. 3,462,765, 3,593,342 and 3,681,786, two-part hinged devices such as that disclosed in U.S. Pat No. 3,466,669, and ball and socket joint devices such as those disclosed in U.S. Pat. Nos. 3,506,982, 3,805,302 and 4,156,296 and British Pat. No. 1,304,837. All of these types of devices have inherent disadvantages; the elastic devices being subject to mechanical failure after only moderate use, while the hinge and ball and socket types exhibit lack of hyperextension and poor adduction.
It has therefore been the principal object of this invention to provide an implantable prosthesis which is particularly suitable for replacement of the metacarpophalangeal and interphalangeal joints and which will provide complete articulation including normal adduction and abduction, flexion and extension.